The invention relates to a method of determining in a non-invasive manner the trade classification, the trade value, the market value and the quality of a body of a slaughtered animal on the basis of optical image processing, which method can preferably be used in slaughterhouses and meat processing works. Generally, larger slaughtered animals, such as pigs, are split along the backbone and suspended on hooks are conveyed by means of special transportation systems between various stations. At predetermined locations the respective halves of the slaughtered pigs are registered, weighed and evaluated.
Within the scope of the evaluation, the body of the slaughtered pig is classified into legal trade classifications on the basis of the muscle-meat percentage. Several methods are permissible for determining the muscle-meat percentage, wherein a measurement of the fat layer (S) and a measurement of the amount of meat (F), measured in each case in millimetres, are set in relation to each other and the muscle-meat percentage (MF %) is calculated by means of an officially established estimating formula.
The values for the terms S and F can be measured in the case of one possible method on a cutlet piece seven centimetres to the side of a line of separation at the level of the 2nd/3rd rib. In another conventional method, the two points (ZP) method, in the case of the pig half created by splitting the carcass along the spinal column the amount of fat (S) is determined at the thinnest site of fat over the Musculus Glutaeus Medius (MGM) and the amount of meat (F) as the thickness of the loin muscle, measured as the shortest connection of the front (cranial end) of the MGM to the upper (dorsal) edge of the vertebral canal.
The muscle-meat percentage (MF %) is determined mathematically specifically for Germany by inserting (S) and (F) into the official formulaMF %=47.978+(26.0429*S/F)+(4.5154*√{square root over (F)})−(2.5018* 1gS)−(8.4212*√{square root over (S)})the value of which is used to determine the trade classification according to the relevant regulations.
The measured values can be determined both manually and also automatically according to the two-point method. A series of documents are known from the prior art and describe the solutions which function automatically for this purpose using optical image processing.
The documents DD 298 310 A5/DE 41 31 556 C2 and DE 41 09 345 C2 describe methods for determining or analysing halves of animal carcasses by means of image processing, wherein the outer contour, layer of fat, meat and back fat ratio are determined, in that images are recorded of the halves of animal carcasses including the backbone and all the intermediate vertebrae layers. As a fixed point for determining the parameters for splitting and classifying the carcass, the starting point is the sacrum of the spinal column, which is also determined in the same way as the other vertebrae by means of object analysis. A disadvantage of this method is on the one hand the high cost of computer technology required to analyse the object using pre-defined contour and object parameters, on the other hand where splitting errors occur during the actual processing, it is not always possible to select the sacrum in a sufficiently reliable manner as a fixed point.
The document DE 197 33 216 C1 describes a method for evaluating halves of slaughtered animals using optical image processing, which renders it possible based on the standard two-point method to classify a carcass using an optical image evaluation of the extended loin region whilst excluding subjective error sources. The accuracy of the estimation for evaluation purposes and thus for classification of the carcass has not been improved thereby in comparison to hitherto known evaluation methods.
A method of evaluating slaughtered animal halves by optical image processing is also known from the document DE 198 47 232 C2, wherein a photogrammetric method is used as a simulation of the conventional two-point evaluation method. In the loin and ham region, two clearly defined points, of which the first point is the body-side end of the pin bone, the second point is the body-side end of the MGM (Musculus Gluteus Medium), and a straight line with the direction of the middle progression of the back fat are recorded photogrammetrically. For actual evaluation purposes, the lengths of partial sections are used which are provided on a perpendicular on the straight line, which is displaced in parallel with the pin bone, at the level of the second clearly defined point through the layer of the back fat. Although in the case of this method the subjective measuring errors of the manually performed two-point method are eradicated, the accuracy of the estimation for evaluation purposes is, however, not substantially increased.
A further method is known from document DE 199 36 032 C1 wherein it is ensured that the quality of halves of slaughtered animals, in particular of slaughtered pigs, is automatically assessed using optical image processing and with respect to the known methods a greater level of reproducible estimating accuracy is achieved which can only be influenced insignificantly by errors during the process of splitting the slaughtered animal and cannot be influenced by optical imaging which is not absolutely perpendicular to the splitting plane, wherein an optical image of the slaughtered animal half in the splitting plane is evaluated in the region of the ham region and loin region photogrammetrically on the basis of specific clearly defined reference points.
The spinal column, the pin bone, the thinnest layer of fat at the MGM and the contours of the back fat in the selected region are used as the clearly defined reference points. The percentage of lean meat which is decisive for assessing the quality is calculated by the summation of part lengths, which are set in ratio with respect to each other and are perpendicular to the straight progression of the canal of the spinal cord in the region of the meat and layer of fat using constants, which are ascertained by means of regression calculations for each term, and a basic constant.
Although within the scope of the method the measured value for the amount of fat (S) is determined in accordance with the legal regulations at correct points, the amount of meat (F) is not determined, as a result of which the muscle-meat percentage (MF %) is not calculated using the official formula, thus classification into the trade classes is not possible.
A method of determining the trade value of the pieces of pig carcasses is known from the document DE 199 52 628 A1, wherein weights, weight and meat percentages of pieces of ham, cutlet, removed cutlet, fillet, shoulder, belly and/or other pieces which can be traded or further processed separately by means of Online—evaluation of pig halves. In order to implement the method, predictors which describe the body structure are determined, which predictors result from the progression of the outer contour of the pig half and, derived therefrom, the area, position and the progression of the spinal column and, derived therefrom, the lengths and areas of part regions of the carcass and one obtained for the pig halves, information regarding the amount of fat and representing the relative thickness and the progression of the approximate total subcutaneous fat layer of the back region. The predictors are set in relation to each other taking into consideration statistical relationships existing between them, as a consequence of which the weight of pieces which are of interest, their weight percentage and meat percentages of the total weight of the carcass are to be determined online in the slaughter line. During the course of the method the complete pig half must be recorded by video and the image object processed and evaluated, which is costly, in order to determine merely the trade value. Owing to the large image region over the entire splitting plane, the rate of evaluation can be impaired and also the weights of pieces cannot be determined in a sufficiently accurate manner.